Method and means for taking cores



April 6, 1943 B. w SEWELL METHOD AND MEANS FOR TAKING CORES Filed Aug. 16, 1940 2 Sheets-Sheet l I IIII/IIIII [If] F G L 6 4 INVENTOR.

ATTORNEY.

April 6, 1943.

B. w. SEWELL METHOD AND MEANS FOR TAKING CORES Filed Aug. 16, 1940 2 Sheets-Sheet 2 6 Y INVENTOR.

BY WM ATTORNEY.

sealed cores.

Patented Apr. 6, 1943 UNITED STATES PATENT oFF cr:

Benjamin W. Sewell, Tulsa, Okla assignor to Standard Oil Development Company} a corporation of Delaware Application August 16, 1940, Serial No. 352,854

The present invention is directed to methods ior obtaining cores and to means adapted to be used in said methods.

It has ions been conventional to the art of drilling bore holes to obtain cores of the formation being penetrated by the bore hole in order to furnish useful geological information.

In the old and well known means and methods employed in recovering the cores the fluids. present in the core under the original formation pressure were not retained, but were largely lost as the core was drawn upwardly to the surface of the earth, and the pressure in the core was gradually diminished.

. In an effort to obtain more complete geological data, pressure core barrels have been constructed which seal the core under the pressure of the formation from which it is cut, and the sealed core is withdrawn to the surface of the earth where the retained fluids are released into suitable containers and tested along with the core in an effort to properly evaluate the characteristics of the formation from which the core has been obtained. Pressure core barrels for carrying out the above described procedure are disclosed in my copending applications Ser. Nos. 269,168 and 310,284. Such pressure core barrels, however, suffer from the disadvantage that they must be designed to have considerable mechanical strength in order to withstand the pressure difierentials to which they are subjected by the This method of construction not only renders the pressure core barrel very expensive, but also requires that the parts thereof be made so large that the diameter of the core obtained is of relatively small dimensions.

It is an object oi. the present invention to provide a method of obtaining cores whereby the fluids originally present in the core under formation pressure maybe obtained by the operator without the use of a core barrel subjected to high internal pressures.

Another object of the present invention is to provide a core barrel used in a hole filled with drilling fluid whereby the drilling fluid is used to form a liquid seal for the gases nd low p fi gravity liquids released from the core as it is withdrawn to the surface of the earth so that the amount of gas and low specific gravity liquids released from the core may be determined by an operator.

Other objects and advantages of the present invention may be seen from a reading of the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a cross sectional view of one modification of apparatus which may be used for carryin: out the present invention;

Fig. 2 is a view of the apparatus appearing in Fig. 1 showing the lower end of the core barrel provided with a means for sealing it in a liquidtight manner;

Fig. 3 is a fragmental cross sectional view of another modification for carrying out the present invention; and

Fig. 4 is a fragmental cross sectional view or still another modification suitable for carrying out the present invention.

Referring specifically to the drawings and first to the modification shown in Figs. 1 and 2, a core barrel III is provided with a tubular body i l which has interlorly arranged in the lower end thereof a core catcher i2 in the manner generally conventional to the art. The upper end of the core barrel is formed with a head 13 for engagement with a conventional fishing tool which is indicated fragmentally as it.

At the upper end of cylindrical body ii is provided a block l5 having a central passage iii controlled by ball valve l1 and spring it. The ball valve is arranged ina cavity is having access to the exterior through slots at.

The core barrels illustrated in the drawing are arranged for use with conventional wire line equipment. The diameters of the barrels are proportioned so that they are held in position to take cores by the pressure developed by the drilling fluid circulated during coring. That is to say, when the operator wishes to take a core, he simply drops the core barrel down the drill stem and begins to circulate drilling fluid. The pressure on the barrel forces the core barrel against a seat in the coring bit and drilling is begun in order to obtain a core. This method of using the pressure of drilling fluid to hold a core barrel in position while taking a core is conventional to the art and no novelty is claimed in the use of this particular feature.

The core obtained enters into the cylindrical passage i i. When it is desired to remove the core barrel containing the core from the bit, this is done in the conventional manner. The rotation v of the core bit and the circulation of the drilling released as the core is withdrawn to the surface, it is desirable to fill the core barrel with liquid before it is inserted in the drillstem so that the only gas present within the core barrel when it is removed from the bore hole will be that released fromthe core.

As the core is cut and enters the. core barrel, excess liquid may "pass upwardly through passages I6 and slot 20. It will be evident that when the core is cut the core barrel will be full of liquid typical of that in the bottom of the hole adjacent to the formation and the hard mineral core.

As the core barrel containing a core is withdrawn to the surface of the earth, the pressure on the liquid with which the hole is filled will gradually diminish and allow the pressure on the core to be correspondingly diminished because the lower end of the cylinder II is in fluid communication with the liquid in the drill pipe. The release of the pressure in the core will allow gas and oil which were retained by the .core under formation pressure to be gradually released. As both the gas and the oil released by the core are of lighter speciflc'gravity than the drilling mud with which the core barrel and drill pipe are filled, they will migrate to the top of the core barrel and cause the drilling mud to be displaced downwardly in the core barrel, the tension on spring l8 being such that the ball i1 seals the passage l6 when there is only a small pressure differential present inside 01' the barrel.

In carrying out the invention it is necessary that the drill pipe contain fluid to its uppermost portion, and in order to more readily use the modification shown in Figs. 1 and 2 it is preferred to place the enlarged section 22 in the top joint of the drill pipe and to keep the level of the mud within this enlarged section, for example, at point 23, as shown in the drawings.

When the core barrel has been withdrawn so that its upper end is exposed to the atmosphere and its lower end is still within section 22 as illustrated in Fig. 1, a cap 24 is arranged on the lower end of cylindrical portion H in order to seal the lower end of the core barrel in a fluidtight manner. The core barrel may then be entirely removed from the drill stem with the contents under a seal and may be removed to I a suitable laboratory testing apparatus where the oil and gas in the core barrel may be displaced and measured in an appropriate manner.

In the modification illustrated by Fig. 3, the core barrel is provided with a partition 25 so that an upper chamber is provided in addition to the chamber II with which the modification illustrated in Figs. 1 and 2 is provided. Partition 25 is provided with with a central passage 21 controlled by a stopcock 28.

In the modification illustrated in Fig. 3 the core is cut and the core barrel withdrawn to the surface of the earth in the same manner as that in the modification previously described, care being taken that the drill stem contains drilling fiuid in order to provide a liquid seal for the lower end of the core barrel. It is not necessary, however, to provide the upper end of the drill pipe with an enlarged section in this modification because, when the upper end of the core barrel is withdrawn to such a point as to expose stopcock 28, the stopcock may be rotated in order to close passage 21. Any gas and oil which has been released from the core as it has drawn upwardly in the drill pipe will have migrated into chamber 26 arranged above stopcock 28 so that the closing of the stopcock will retain these fluids in the upper portion 0! the A core barrel. The core barrel may then be removed i'rom the hole without care being taken to preserve the fluid surrounding the core barrel. The core may then be removed for examination in the-usual manner and the gas and oil displaced from the chamber 26 and measured-to determine the amount of'fluid which was released irom the core as its pressure diminished from formation pressure to substantially atmospheric pressure.

In the modification illustrated in Fig. 4, the core barrel is provided with apartition 29 provided with passage 30 and a transparent tube 3| is arranged in the upper end of the corebarrel between passage 30 and passage l8. The

A core barrel is provided with slots 32 to allow the transparent tube to be visible to the operator. Transparent tube 3| may be provided with suitable graduations, if desired. It is sometimes advantageous to provide passage 30 with a stopcock 28 in order to seal the transparent tube 8| independently of passage II.

In the modification shown in Fig. 4 the core is cut and drawn upwardly in the drill stem in the manner described in the previous modifications. The gases and liquid hydrocarbons released from the core as its pressure is gradually diminished migrate upwardly and accumulate in the transparent tube 3|. The drill stem is kept full of fluid so that the upper end of the core barrel may be exposed to the atmosphere, while the liquid seal is retained about the lower end of the core barrel. The amount of gas and oil accumulated in transparent tube 3! may be read off directly, while the lower end of the core barrel is still submerged in the drilling fluid in the drill pipe. After such a reading is made, the liquid and gas may be retained by closing stopcock 28 or by the use of a cap, as shown in Fig. 2, if desired, but sometimes the reading through tubing 3| is sufiicient and no attempt is made to retain the fluid accumulated in tubing 3!. By the use of the device illustrated in Fig. 4 relatively rapid determinations may be obtained.

The core barrels illustrated in the drawings are arranged to be held in position for taking a core by means oi the pressure of the drilling fluid, but it will be evident that other means may be used for holding the barrel in position, while coring. For example, one of the known means of looking a core barrel in position is by means of a locking dog built into the core barrel as a part thereof and arranged to cooperate with a suitable mechanism with which the bit head is provided. Obviously, the core barrel herein described may be provided with such a locking means or other locking means which are known to the art or may hereafter be developed.

While I have disclosed specific modifications for carrying out the present invention, it will be apparent to a skilled worker that other means may be used for accomplishing the same or similar results. For example, while I have disclosed means suitable for use with wire lines, it will be readily apparent that the same equipment may be arranged for use in core barrels which are attached in drill stems. It is accordingly not my intention to be bound by the specific modifications disclosed, but to claim the invention as broadly as the prior art permits.

I claim:

1. A device for obtaining cores comprising, in combination, a body adapted for longitudinal parent cylinder arranged in said .body having its lower end in fluid communication with said passage, and its upper end provided with a closure.

2. A device adapted for longitudinal movement in a drill stem attached to a core bit for receiving a core cut by the bit, comprising, in combination, a body defining an elongated cavity open at its lower end for receiving a core cut by the bit, means arranged in the lower portion of said body for retaining a core in the cavity without closing the opening, apassage fluidly connecting the upper end of said cavity with the exterior,

means preventing the flow of fluid into the cavity through said passage and for allowing flo from the cavity to the exterior when the pressure within the cavity exceeds that in the borehole adjacent the chamber by a predetermined amount, a partition separating said cavity into an upper and a lower portion,.a passage piercing said partition 01 a restricted size to prevent the passage of a core from the lower to the upper portion of said cavity, and a valve controlling the flow of fluid through said passage.

3. A device adapted for longitudinal movement in a drill stem attached to a core bit and for receiving a core cut by the bit comprising, in combination, a body deflning an elongated cavity at its lower end for receiving a core cut by the bit, means arranged in the lower portion of said body ior'retaining a core in the cavity without closing the opening, a transparent member secured to said body to define a chamber above said cavity, a passage or restricted area connecting said chamber and said passage to prevent a core from passing from the cavity into said chamber, a passage connecting the upper portion of said chamber to the exterior, and a valve controlling said passage to allow the flow oi fluid from the chamber to the exterior when the pressure becomes greater in the chamber than in the borehole adjacent said chamber by a predetermined amount.

4. A method of coring comprising the steps of cutting a core in aborehole which contains fluid, moving said core upwardly in said borehole while maintaining it constantly under a liquid seal of fluid in the borehole, segregating and retaining gases which are released from the core as it is raised in the borehole, sealing the core and the retained gases and liquids in a gas tight manner when the core reaches the surface, and measuring the amounts or segregated liquids and gases so retained.

5. A device adapted for longitudinal movement in a drill stem attached to a core bit for receiving a core cut by the bit comprising, in combination, a body defining an elongated cavity at its lower end for receiving a core cut bythe bit, means arranged in the lower portion of said body for retaining a core in the cavity without closing the opening, a passage in the upper end of said body arranged to release fluid from said cavity when the pressure in the cavity is greater than that of the liquid in which it is immersed by a predetermined amount and for retainnig fluid in the upper end of the cavity when the pressure in the cavity is only slightly greater than that outside oi said body, and a stopcock arranged in the lower portion of said passage.

6. A device adapted for longitudinal movement in a drill stem attached to a core 'bit for receiving a core cut by the bit comprising, in

combination, a body defining an elongated cavity at its lower end for receiving a core cut by the bit, means arranged in the lower portion of said body for retaining a core in the cavity without closing the opening, a passage in the upper end 01' said body arranged to release fluid from said cavity when thepressure in the cavity is greater than that oi the liquid in which it is immersed by a predetermined amount and for retaining fluid in the upper end 01' the cavity when the I pressure in the cavity is only slightly greater than that outside of said body, and a transparent tube arranged in the upper portion of the barrel in fluid communication with said passage.

BENJAMIN W. BEWELL. 

